The invention concerns the transmission of digitized vocal signals and, more particularly, a process, and a corresponding device, of vocal interpolation in a transmission system of digitized voice.
Numerous transmission needs of telephony by radio presently exist, both for civil and military applications. The tendency is to effect these transmissions under digital form, this type of transmission allowing to regenerate the signals, the coding, and also allowing a digital numbering or complex processing of the vocal signal.
In the ranges of frequencies used, VHF and UHF, vocal coding is of the DELTA type, i.e. a coding resulting from a differential quantification of the analogous signal on two levels giving direct rise to a digital message. Several variants of this coding are used; the output most commonly used being 16 kbits/sec.
In radio transmission, numerous phenomena can disturb the transmission. In classic radiotelephone type transmissions, the transmissions occur at fixed frequency and are subject to packs of errors or to pulse interferences, for example, those created by vehicle engines. In civil or military radiotelephone transmissions using the frequency jump, a group of frequencies is used, each of these frequencies acting as transmission support during a brief period of time called "stage". Certain "stages" can be disturbed or jammed by the unintentional or voluntary presence of other emissions on the corresponding frequency(ies).
In the presence of such disturbances, the DELTA coded vocal signal is restored with transitory phenomena which are most disagreeable for listening comfort and which render the transmission unintelligible when the occurence probability of these phenomena increases.